DESCRIPTION: (Applicant's Abstract) This application proposes to study signalling through dopamine receptors. Recent data suggests that G protein-coupled receptors, G proteins and effectors co-localize within microdomains of the plasma membrane. Co-localization may influence receptor expression, coupling and desensitization. To characterize these interactions, the investigator has used the third cytoplasmic domain of the D2 dopamine receptor as bait in the yeast two-hybrid system and identified the actin-binding protein spinophilin, which also contains PDZ and coiled-coil domains. The long-term goal of this application is to determine the function of the dopamine receptor-spinophilin interaction. The program involves characterization of the signalling complex, localization of spinophilin in the brain and analysis of its functional effect on dopamine signalling. After mutagenesis to map the sites of interaction in spinophilin and the receptor, mutant spinophilin or receptor will be introduced into cells and the effect on dopamine receptor function assayed. The results have relevance for dopamine and probably other signalling systems, and may illuminate defects in signal transduction that contribute to human disease.